Compressors used in refrigeration, air conditioning and heat pump systems are normally mounted to the associated base pan through a vibration isolating mounting assembly. Specifically, compressors are commonly mounted to the base pan of a window room air conditioner, of a display case unit, of a split unit with the compressor indoors, or of a condensing or outdoor unit. In such installations, it is desirable to damp vibrations and the resultant noise caused by operation of the compressor. A common arrangement is to locate elastomeric grommets between the base or feet of the compressor and the base pan upon which it is mounted. The grommets are attached to the compressor feet and the compressor, with attached grommets, is set on the base pan. Threaded studs (with sleeves) are then pushed through the grommets to secure the connection.
The grommets support the weight of the compressor and are radially spaced from the center of gravity of the compressor to prevent it from tipping. While the spaced supports provide stability, they also increase the torsional restoring forces due to their distance from the axis of rotation. The grommets serve to vibrationally and acoustically isolate the compressor from its support. The resonance frequencies of the compressor torsional and rocking modes are inherently high in such a mounting arrangement, tending to fall into the proximity of the compressor speed and to cause vibration and noise problems. To alleviate these problems, the grommets are normally made very soft in the transverse directions which may result in excessive movement during shipping. Excessive movement during shipping can cause damage to the compressor and/or its connections to the other components in the system.